A radiosonde (Sonde is French and German for probe) is a unit for use in things such asweather balloons that measures various atmospheric parametersand transmits them to a fixed receiver. Radiosondes may operate at a radio frequency of 403 MHz or 1680 MHz and both types may be adjusted slightly higher or lower as required. A rawinsonde is a radiosonde that is designed to only measure wind speed and direction. Colloquially, rawinsondes are usually referred to as radiosondes.

Modern radiosondes measure or calculate the following variables:

• Pressure
• Altitude
• Geographical position (Latitude/Longitude)
• Temperature
• Relative humidity
• Wind (both wind speed and wind direction)
• Cosmic ray readings at high altitude

Radiosondes measuring ozone concentration are known as ozonesondes.

Some photo taken during the search of a radiosonde.